1. Field of the Invention
The present invention relates to a grounding apparatus for use in a system in which a power conditioner converts the DC power generated in a DC power source, for example, a solar cell, to an AC power to be supplied to an AC power system, the grounding apparatus being provided between the ground and the AC positive bus or AC negative bus connecting the solar cell and the power conditioner.
2. Description of the Related Art
Patent Literature 1 discloses a power supply apparatus configured to supply the DC power from, for example, a solar cell to a grounded load. The power supply apparatus has a power supply means, a first output switch, a grounding fault detection circuit, and a control means. The power supply means has non-insulated power input and output terminal for supplying power to the grounded load. The first output switch is configured to connect or disconnect the power supply means to or from the grounded load. The impedance means is provided between the ground potential and a point near the power input terminal of the power supply apparatus. The grounding fault detection circuit has a voltage or current detection means and a ground switch. The control means is configured to control the first output switch and the grounding fault detection circuit. If the control means opens the first output switch and closes the ground switch, the grounding fault detection circuit detects a change in the main voltage at a point other than the grounded load, thus detecting a grounding fault, from the voltage or from the current detected by the current detection means.
So configured as described above, the apparatus disclosed in Patent Literature 1 can detect the grounding fault without connection to the grounded load.
Patent Literature 2 discloses an interconnection inverter in which a converter circuit and an inverter circuit, not insulated from each other at the out of the former and the input of the latter, convert DC power to AD power, and which outputs the AC power to a system connected to it. The interconnection inverter comprises a DC grounding fault detection means for detecting the grounding fault of the solar cell. The interconnection inverter further comprises a control means for controlling either the input voltage or the intermediate voltage between the converter circuit and the inverter circuit is controlled, either raising or lowering the voltage, thereby setting the ground potential of the solar cell to a value other than a near-zero potential. Thus, the grounding fault detected is a change in the main current.
In the interconnection inverter discloses in Patent Literature 2, described above, the control means controls the input voltage or the intermediate voltage, raising or lowering the voltage, ultimately setting the ground potential of the solar cell to a value other than a near-zero potential. Therefore, any grounding fault of the solar cell can be reliably detected.